A Massachusetts judge will decide later this month whether to dismiss charges against a Lynn man accused of kidnapping his 5-year-old son and lying to investigators about the disappearance.

Russell Sobelman, a lawyer for Ernesto Gonzalez, said in Essex County Superior Court in Salem on Tuesday that under state law charges should be dismissed against defendants who have been declared incompetent if they have served at least half the maximum sentence they would have received if convicted.

Prosecutor Jean Curran countered that a dismissal for Gonzalez would be "premature," arguing that the clock should start running from the date he was ruled incompetent last year.

Gonzalez has been behind bars since his son, Giovanni, disappeared in August 2008 during a weekend visit. His mother, Daisy Colon has said she believes her son is alive and being hidden by friends of Gonzalez.

Several months after his arrest, Gonzalez told Boston Globe reporter that he had killed Giovanni and disposed of his body parts in trash containers throughout the city. No trace of the boy was found and no additional charges were filed against Gonzalez.

Sobelman said in court his client has never been competent. He said Gonzalez's mental health condition is "deteriorating" and not likely to improve despite stronger medication and even electric shock treatments.

He said Gonzalez would not be released anytime soon because of two other pending criminal cases in alleged attacks on a fellow inmate and a guard. Sobelman said Gonzalez also is confined to Bridgewater State Hospital under a civil commitment.

Colon has said she believes Gonzalez has been playing the system, and worries that if the charges are dismissed, they won't be reinstated even if he is later found competent.